I don't eat jam. My wife doesn't eat jam. Kitty doesn't eat jam. The dog doesn't eat jam. Despite that there is always a jar of jam in the fridge, but I have never seen jam go mouldy. Tomato paste, my heavens yes, as soon as you take your eyes off it. Jam never.

Eventually somebody decides they're sick of moving that fecking jar of jam whenever they're looking for a jar of something they actually want, and bins it. Yet soon enough somebody thinks they want jam, when actually they crave the sweet release of death, or something, or we're expecting visitors ("Oh! Do we have jam? They'll probably want jam."), and a jar is purchased, opened, quickly closed, and refrigerated as per the label's instructions.

Perhaps Theresa May is just being overly literal about the instructions, and refrigerating after opening without actually reading between the lines and closing it also. Still, aren't we all just yesterday's jam?